1.1 Systems Architecture

Question 1

Registers of a CPU

Answer 1

1) PC (program counter): holds the address of the next instruction to be processed

2) MAR (Memory address register): holds address of the instruction to be fetched

3) CIR (current instruction register): holds the current instruction in use

4) MDR (memory data register): holds data that has been fetched or is to be sent to/from memory

5) ACC (accumulator): holds the result of the calculation carried out in the ALU

Question 2

Components of a CPU

Answer 2

1) Control Unit: controls the flow of data inside the cpu. Decodes and executes instructions

2) arithmetic logic unit: performs all logical and arithmetic functions

3) Memory unit: this is the CACHE memory

Question 3

Factors that can affect cpu performance

Answer 3

1) clock speed: the clock controls number of times the fetch execute cycle is performed per second. Faster clock speed, more instructions are completed. Measured in hertz

2) number of cores: each core can process an instruction with each fetch execute cycle. More cores means that more instructions can be carried out at the same time

3) cache size: cache is super fast memory close to the cpu. It holds frequently and recently used data. A larger cache gives the cpu faster access to more data

Question 4

Describe fetch decode execute cycle

Answer 4

Fetch: copy memory address from program counter to Mar. Copy instruction stored at Mar address to Mdr. Increment program counter by one to point at the next instruction

Decode: instruction in mdr is decoded by the control unit

Execute: instruction is performed by the control unit. This may include calculations being completed by the alu. The results of calculations will be held in the accumulator